Failing to invoke web service after upgrading app from .NET1.0 to .NET1.1

I have a working VB.NET2002 (.NET1.0) app that talks to a Websphere webservice. The development machine is Windows 2000 (sp4). The client-side app runs on a Citrix server, also Windows 2000 server (sp4).

My app has a proxy class that uses SoapRpcMethodAttribute of SoapHttpClientProtocol to make an RPC call. The proxy class submits a SOAP request and gets a SOAP response in the form of an XML string.

The app worked OK until I upgraded to VB.NET2003 (.NET1.1). Now I get the following error when I deploy it to the Citrix machine:

"The request was aborted: The request was cancelled. at system.Net.ConnectStream.CloseInternal(Boolean internalCall, Boolean ignoreShutDownCheck)
at System.Net.ConnectStream.CloseInternal(Boolean internalCall) at System.Net.ConnectStream.Close()
at Stste.Web.Services.Protocols.SoapHttpClientProtocol.Invoke(String methodName, Object[] parameters)
at GTPSMessagingLib.GTPSRouterService.process3ParmRequest(String inputHeader, String messageControlPayload, string inputMessage)
at GTPSMessagingLib.GTPSMessenger.Process3ParmRequest(String psHeader, String psMCP, String psPayload, String psResponse)"

Please Note:
The response comes back perfectly when app is run in Debug mode on the development machine.
Please help. Is there anything I'm missing? I'm pulling out my hair on this one.

The proxy class I use in the app is:

'------------------------------------------------------------------------------
' <autogenerated>
' This code was generated by a tool.
' Runtime Version: 1.1.4322.2032
'
' Changes to this file may cause incorrect behavior and will be lost if
' the code is regenerated.
' </autogenerated>
'------------------------------------------------------------------------------

Option Strict Off
Option Explicit On

Imports System
Imports System.ComponentModel
Imports System.Diagnostics
Imports System.Web.Services
Imports System.Web.Services.Protocols
Imports System.Xml.Serialization

'
'This source code was auto-generated by wsdl, Version=1.1.4322.2032.
'

'<remarks/>
<System.Diagnostics.DebuggerStepThroughAttribute(), _
System.ComponentModel.DesignerCategoryAttribute("code"), _
System.Web.Services.WebServiceBindingAttribute(Name:="GTPSRouterServiceSoap", [Namespace]:="urn:ServiceRequest")> _
Public Class GTPSRouterService
Inherits System.Web.Services.Protocols.SoapHttpClientProtocol

'<remarks/>
Public Sub New()
MyBase.New
Me.Url = "http://localhost/GTPSRRWebService/GTPSRouterService.asmx"
End Sub

'<remarks/>
<System.Web.Services.Protocols.SoapRpcMethodAttribute("urn:ServiceRequest/process3ParmRequest", RequestNamespace:="urn:ServiceRequest", ResponseNamespace:="urn:ServiceRequest")> _
Public Function process3ParmRequest(ByVal inputHeader As String, ByVal messageControlPayload As String, ByVal inputMessage As String) As String
Dim results() As Object = Me.Invoke("process3ParmRequest", New Object() {inputHeader, messageControlPayload, inputMessage})
Return CType(results(0), String)
End Function

'<remarks/>
Public Function Beginprocess3ParmRequest(ByVal inputHeader As String, ByVal messageControlPayload As String, ByVal inputMessage As String, ByVal callback As System.AsyncCallback, ByVal asyncState As Object) As System.IAsyncResult
Return Me.BeginInvoke("process3ParmRequest", New Object() {inputHeader, messageControlPayload, inputMessage}, callback, asyncState)
End Function

'<remarks/>
Public Function Endprocess3ParmRequest(ByVal asyncResult As System.IAsyncResult) As String
Dim results() As Object = Me.EndInvoke(asyncResult)
Return CType(results(0), String)
End Function
End Class